the buttons for next or prior titel in the lighning app is the symbol usually says “fast forward/backward”, but not start/end or skip. The classic symbol like on CD players or old tapedeckes for that is the single arrow with a vertical bar.
This is cosmetic only, but to get closer to perfection that should be no problem to correct.

Interesting, we had a discussion about the icon back to year 2013 when our team started design the UI of Lightning DS. I did raised the question about these icons. The answer I got is they feel |<< and >>| does not look nice and most people know what function it is, so we got keep the << and >> option till now…